Delayed onset muscle soreness — the kind that leaves you wincing as you walk down the stairs after squat day — is pretty common after your first day of a new workout. But it’s not as likely to happen after the second day, thanks to a phenomenon known as the repeated bout effect.
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Essentially, a soreness-inducing workout seems to give you some protection from additional soreness that lasts for a good while. (It fades over time, but research suggests some amount of protection can last for months.) If you’ve ever followed a friend to the gym and done their workout with them, you’ve seen this in action. You may be sore for a week, but since they do this same workout all the time, they barely feel a thing.
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